Power in Step down Transformer
The power in a transformer is measured using the product of voltage and current. The power in a transformer is rated in Volt â Amps VA (or Kilo Volt â Amps kVA for larger transformers).
Ideally, the power in any transformer is constant i.e. the power available at the secondary of the transformer is same as the power at the primary of the transformer.
This is even applicable to a step down transformer. But, since the voltage at the secondary of a step down transformer is lesser than that at the primary, the current at the secondary will be increased in order to balance the total power in the transformer.
Current and Voltage Relation in Step Down Transformer
We will now see how this works. Let VP be the voltage at the primary, IP be the current at the primary and PP be the power at the primary side of the transformer.
We know that the power can be calculated by simply multiplying the voltage and current. Hence, the power at the primary side of the transformer is given by